Antibiotic assays



  • Therapeutic drug monitoring is required for certain anti-infective agents in order to ensure appropriate serum levels have been achieved. The purpose is to ensure therapeutic levels have been attained and to minimise toxicity.
  • Routinely available assays include:
    • Amikacin
    • Flucytosine
    • Itraconazole
    • Posaconazole
    • Voroconazole


  • Therapeutic levels for these agents are shown in the table later on this page.
  • Other anti-infective agents may be assayed on request. Please discuss with the Consultant Microbiologist prior to obtaining any samples. Comments on the interpretation of assay values will included in the report.
  • Blood samples from HIV positive patients must be heat treated before they are sent to the reference laboratory.  Please ensure that the laboratory is informed if samples are from an HIV positive patient.
  • See also:


Result interpretation

  • Results are reported with a standard interpretative comment that gives the recommended target (normal) levels
  • If there is any doubt regarding interpretation, contact the Consultant Microbiologist


Sample requirements

Serum - refer to the table below for collection requirements

8.5ml of blood taken into a plain gel tube

8.5mL BD Vacutainer tube


Agent When to collect
IV amikacin once daily See antibiotic guidelines
IV amikacin BD/TDS See antibiotic guidelines
Oral flucytosine pre-dose and 2 hours post-dose
IV flucytosine pre-dose and 30 minutes post-dose
Oral or IV itraconazole pre-dose after 7 days
Oral posaconazole pre-dose after 5 days
Oral voriconazole pre-dose after 3-5 days


Required information

  • Dosing regime
  • Date and time of last dose
  • Date and time of sample(s)
  • HIV status


Store at fridge temperature

Transport as soon as possible at ambient temperature

Turnaround time

Sent to a to a Regional Reference Centre.

Up to 5 days

Page last reviewed: 23/07/2015